Some other tips: You can use a little light to see if you can visibly see the dust on the sensor. If you buy a blower, don't stick the tip right beside the sensor. Most dust will easily fall off even if you blow from a bit of a distance. And third, stick the body upside down with the sensor facing down so you the dust will theoretically fall down.

So the line is a dust "spot"? Were you able to locate them?

Try to take photo against white wall, sky...etc that is plain single color. Use blower to blow the dust in those area and repeat taking photo until it is gone.